Pemphigus foliaceus is an auto-immune disease which results from autoantibodies forming against the proteins responsible for holding the keratinocytes together in the epidermis. The result is a loss of cohesion and the formation of pustules just below the stratum corneum. P. foliaceus is part of the pemphigus complex. Sixty percent of the cases have been seen in Appaloosas, with lesser numbers of Thoroughbreds then other breeds.
Signs
The primary lesion is a superficial pustule which rapidly ruptures. This causes alopecia scaling and crusting. Other signs include lethargy, dependent oedema, pyrexia, and pruritus. The disease begins on the face, head, and lower extremities, and spreads to the entire body.
Diagnosis
A skin biopsy is essential for the diagnosis. The ideal lesion to biopsy is a pustule, but crusts can also yield a diagnosis. The characteristic histopathological finding is subcorneal pustules with acantholytic cells. Immunostaining can also be done but is usually not necessary.
Treatment and Prognosis
Being an autoimmune disease the treatment centres on immunosuppression. Typically oral prednisolone is used at high dose (2 mg/kg PO BID) to start, and slow reduction to an every other day dosing regimen. Azathioprine (2 mg/kg q 48 hrs) can be used concurrently and allows for a lower dosage of prednisolone.
Gold salts which have also been used successfully in the horse. It involves weekly intramuscular injections (1 mg/kg). The first two weekly dosages are small (e.g. 50 mg) to ensure the animals will tolerate the drug. When the disease is in remission the frequency of administration can be decreased to q 2-4 weeks. This therapy is less commonly used because of the potential for serious adverse side effects.
Young animals have been treated for several weeks and then therapy was stopped with no relapses. Adults usually require treatment for life.
Tags: Dermatology